1. Field of the Invention
The invention relates to medical devices, and, more particularly, to an implantable medical device system for providing ECG data without the use of external electrodes.
2. Description of the Related Art
Surface ECG tracings are routinely collected during a clinical follow-up visit of a patient having a cardiac pacemaker or implantable cardioverter defibrillator (ICD). The ECG tracings allow a clinician to observe electrical activities corresponding to the patient's heart rhythm, i.e. observe whether the rhythm is an intrinsic, normal sinus rhythm, or if the atrium and/or ventricles are being paced. The ECG tracings can also be analyzed for evidence of pacing capture, fusion, examined for changes due to ischemia, and used for measuring the duration of the P-wave and QRS-complex.
Acquisition of surface ECG tracings requires considerable preparation time. During an office visit, the patient is generally required to partially disrobe, and the surface ECG electrodes, typically 3 to 12, are placed on the skin at appropriate locations. The electrodes are then connected to an ECG monitor to first verify proper connection and then for observation or recording of the ECG traces. Sometimes patients are monitored through transtelephonic follow-ups. A surface ECG may be monitored transtelephonically by having the patient self-apply wrist or fingertip electrodes. Transtelephonic follow-ups are convenient for the patient since the patient does not need to travel to a clinic. Unfortunately, the quality of ECG signals so obtained is often poor.
Recently, remote patient monitoring systems have been introduced which allow data from an implantable medical device (IMD) such as a pacemaker or ICD to be uplinked telemetrically to a home monitor and transferred to a web-based patient management system accessible by an Internet-enabled computer. Such systems allow physicians to observe data retrieved from an IMD and manage the IMD performance and patient care independent of the patient's location. Remote patient management systems thereby reduce the time burden and inconvenience posed upon both the patient and the clinician normally associated with follow-up visits performed in a clinic. Long-range telemetry systems that enable the IMD to communicate with the home monitor without any patient intervention are proposed, making remote patient management even more convenient to the patient. However, if ECG tracings are desired during a remote follow-up session, the patient would be required to self-apply surface electrodes and such data would need to be transferred to the remote patient monitoring system.
ECG data made available without the use of surface ECG electrodes would clearly benefit the clinicians, nurses or other medical technicians and the patient by simplifying clinical follow-up visits and reducing the time required. Furthermore, ECG data made available without the use of surface ECG electrodes would allow remote patient follow-up sessions to be more complete without added burden to the patient.